The invention relates to an injection module, in particular to an injection module for injecting a reducing agent into the exhaust tract of an internal combustion engine, and to an exhaust tract equipped with an injection module of said type.
SCR (“selective catalytic reduction”) with a urea-containing reducing agent (“AdBlue®”) is a proven technique for the denitrogenization of the exhaust gases of diesel engines. Here, the liquid reducing agent is injected in finely atomized form into the exhaust-gas flow upstream of a reducing agent catalytic converter.
To achieve a high level of conversion of the nitrogen oxides with the least possible reducing agent slippage, the reducing agent must be distributed over the catalytic converter inlet surface as homogeneously as possible. This is achieved either by way of mixers fitted in the exhaust pipe or by way of a long mixing path to the catalytic converter from the location at which the reducing agent is dosed in.
DE 44 17 238 A1 discloses a device for the reduction of nitrogen oxides in the exhaust gas of an internal combustion engine, having an inlet chamber, having a hydrolysis catalytic converter, having a DeNOx catalytic converter and having an oxidation catalytic converter, wherein the inlet chamber, the hydrolysis catalytic converter, the DeNOx catalytic converter and the oxidation catalytic converter form a substantially cylindrical unit through which the exhaust gas can flow in the stated sequence, and the diameter of the inlet chamber is greater than the diameter of the hydrolysis catalytic converter. It is achieved in this way that the exhaust gas that is mixed with a reducing agent in the inlet chamber enters the catalytic converters with a homogeneous reducing agent distribution and with an exhaust-gas flow density which is as homogeneous as possible over the cross section of the exhaust tract.
To realize the required homogenization of the reducing agent with the exhaust gas, a reducing agent spray mist (“spray”) is required which, as far as possible, is flat but covers the full area. To avoid deposits of the reducing agent in the exhaust system, it is necessary that only a limited amount of the reducing agent impinges on the walls of the exhaust system.